The exotic musical influences that the group were exposed to in Fez inspired them to pursue a more experimental sound, but as the sessions unfolded, the band decided to scale back the extent of those pursuits.

[1] After U2 guitarist the Edge worked individually with Rubin in Los Angeles,[2] the group spent two weeks in September 2006 completing songs with the producer at Abbey Road Studios in London.

[3] Later that year, the band released two songs from these sessions on the compilation album U218 Singles: a cover of the Skids' "The Saints Are Coming" with Green Day, and "Window in the Skies".

[2][9] Bono also invited Eno and Lanois, hoping they would collaborate with the band as full songwriting partners in recording an album of "futuristic spirituals" or "future hymns"—songs that would be played forever.

[15] The songs "Moment of Surrender", "White as Snow", "No Line on the Horizon" and "Unknown Caller" were written at this time; each track was recorded in one take.

[23] In November 2008, the Edge confirmed the album's working title as No Line on the Horizon and noted that the band had to move quickly to complete mixing to meet the new February release date.

The group had planned to release the material as two extended plays, titled Daylight and Darkness, but during these sessions decided to compile the best songs onto one album.

[31][33] At the end of the sessions, the band chose to include "White as Snow", a quiet song about a dying soldier in Afghanistan, to balance out the earlier, rockier tunes.

[44] The Songs of Ascent project ultimately did not come to fruition and has not been released; its evolution and apparent abandonment are examined in the book The Greatest Albums You'll Never Hear.

The band appeared the same day at an Apple Inc. product launch event to announce the album and reveal it was being released to all iTunes Store customers at no cost.

"[12] Although each character tells a personal story, the underlying theme of the album is peripheral vision, events taking place in the wider world, "just at the edges".

The lyrical idea of a place "where the sea meets the sky and you can't tell the difference between the two" and the vocal delivery were both present from the start.

The band wanted a track that felt euphoric, and the melody, created from a series of chord changes during a jam, was worked on continuously by Bono.

[9] Eno noted, "Apart from some editing and the addition of the short cello piece that introduces it, the song appears on the album exactly as it was the first and only time we played it.

In "Unknown Caller", the character is suicidal and, while using his phone to buy drugs, begins receiving cryptic text messages with technology-inspired directions.

[26] Universal Music Group took extreme measures to prevent the album from leaking, offering pre-release listening sessions for critics instead of sending out review copies.

"[57] Continuing the mathematical theme that the equals sign established, the packaging of the digipak special edition features a "little hidden code" in the form of a piece of the Fibonacci sequence.

The plot focuses on a Parisian motorcycle officer, played by Saïd Taghmaoui; the character has become disillusioned with his life and the conflict between immigrants and the police in the city, causing him to leave to see his girlfriend in Tripoli.

[83] David Fricke of Rolling Stone gave it a five-star score and called it "[U2's] best, in its textural exploration and tenacious melodic grip, since 1991's Achtung Baby.

"[89] In his review for Blender, Rob Sheffield stated "The days are gone when U2 were trying to keep it simple—at this point, the lads have realized that over-the-top romantic grandiosity is the style that suits them, so they come on like the cosmic guitar supplicants they were born to be.

"[93] Jeff Jensen of Entertainment Weekly graded it an "A−" and called the album "an eclectic and electrifying winner, one that speaks to the zeitgeist the way only U2 can and dare to do.

"[94] BBC Music reviewer Chris Jones said, "There's plenty to rejoice about here" while noting that the "symbiotic relationship with Brian Eno (and Daniel Lanois) seems to have reached the point of imperceptibility.

"[95] NME contributor Ben Patashnik called the album "a grand, sweeping, brave record that, while not quite the reinvention they pegged it as, suggests they've got the chops to retain their relevance well into their fourth decade as a band.

"[91] Pitchfork reviewer Ryan Dombal gave a score of 4.2 out of 10, stating, "the album's ballyhooed experimentation is either terribly misguided or hidden underneath a wash of shameless U2-isms.

"[87] Cameron Adams of the Herald Sun gave a rating of three and a half stars, comparing it to the 1990s albums Zooropa, Pop, and Original Soundtracks 1 while stating "This is no blockbuster ...

[96] Madeleine Chong of MTV Asia wrote that, "Although U2 should be lauded for their efforts at constant reinvention and pushing the envelope in the rock genre, [No Line on the Horizon] possesses neither the iconic qualities of The Joshua Tree or the radical yet relevant magnetism of Achtung Baby.

[113] The album did not generate a hit single;[112] ABC noted that sales of How to Dismantle an Atomic Bomb had been propelled by the track "Vertigo, which had become well known to the public from its use in iPod commercials.

[123] In 2010, U2's scheduled headline appearance at the Glastonbury Festival 2010 and their North American leg were postponed until the following year after Bono suffered a serious back injury.

[112] He noted that the reaction to the songs in the live setting made U2 believe that the material was connecting with the fans, adding, "There's a lot of records that make great first impressions.

[136] While he considered "Moment of Surrender" to be perhaps U2's best song of the 2000s, Bono said he believes No Line on the Horizon was flawed because "the progressive-rock virus had crept in", adding: "The discipline of our songwriting, the thing that made U2 — top-line melody, clear thoughts — had gone.